The invention relates to a road sweeper with a rotatingly drivable sweeping brush and a sweepings container as well as a suction blower which is in flow communication with the sweeping brush via a suction conduit and an intake duct for the purpose of taking in dust-containing air, and with at least one filter for separating dust from the air drawn in, wherein the at least one filter can be acted upon on the clean side with external air, which is stored in a pressure container and is subject to pressure, via at least one external air valve for the purpose of cleaning.
Road sweepers of this type are known, for example, from DE 26 29 967 A1. With their aid, a ground surface to be cleaned can be swept, wherein coarse sweepings are transferred into the sweepings container by means of the rotatingly drivable sweeping brush. Sweeping of a dry ground surface often results in a considerable generation of dust. In order to counteract this, the road sweeper has a suction blower which is in flow communication with the sweeping brush via a suction conduit and an intake duct. With the aid of the suction blower, dust-containing air can be drawn in so that the generation of dust during sweeping of the dry ground surface is kept low. On its way from the sweeping brush to the suction blower the air drawn in flows through a filter for the purpose of separating dust. The filter becomes clogged during the course of time and must, therefore, be cleaned off after a certain time. For this purpose, the road sweeper has a pressure container, in which air subject to pressure is stored and from which the air can be supplied via an external air valve to the clean side of the filter, i.e. the side of the filter facing away from the sweepings container. The external air subject to pressure flows through the filter contrary to the direction of flow of the air drawn in which prevails during normal sweeping operation. As a result, the filter will be cleaned off.
In the case of the road sweeper known from DE 26 29 967 A1, a plurality of filters are used which are each configured in the form of a filter cartridge. One air pipe is associated each time with eleven filter cartridges and this extends above the filter cartridges and has essentially in the center of the filter cartridges openings or nozzles, via which the filter cartridges can be acted upon with external air. The external air is supplied to the air pipes from a pressure container in the form of an air distribution pipe via a magnetic valve. The pressure in the air distribution pipe is more than 7 bar and each magnetic valve is opened for a period of time of 0.1 seconds. As a result, a common stream of air is supplied to a respective eleven filter cartridges and this flows through the associated air pipe.
The fact that an effective cleaning of the filter is guaranteed only when a considerable amount of external air flows through the filters has proven to be disadvantageous in the case of the road sweeper known from DE 26 29 967 A1. This large amount of external air must, subsequently, be drawn off again by the suction blower, namely within a very short period of time since, otherwise, there is the risk of the external air exiting from the road sweeper via the intake duct in the area of the sweeping brush. This would increase the generation of dust which is to be avoided.
The object of the present invention is to further develop a road sweeper of the type specified at the outset in such a manner that the at least one filter can be cleaned off effectively with as small an amount of external air as possible.